CA1048319A

CA1048319A - Method and apparatus for shaping an airfoil

Info

Publication number: CA1048319A
Application number: CA75237186A
Authority: CA
Inventors: Eugene J. Malinowski; Raymond J. Zyck
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1974-10-23
Filing date: 1975-10-07
Publication date: 1979-02-13
Also published as: JPS6010846B2; JPS5182483A; FR2289293A1; IT1043417B; DE2545565A1; SE419188B; FR2289293B1; IL48235A; DE2545565C2; US4149449A; SE7511838L; US4015509A; GB1519219A; IL48235A0

Abstract

ABSTRACT
An improved apparatus is utilized to shape the lead-ing and trailing edges of a tapered airfoil having twisted and bowed major side surfaces. To compensate for taper, a rotatable forming tool is moved inwardly toward the longitudinal axis of the airfoil as the tool is moved through a working stroke along an edge of the airfoil. To compensate for the bowed side sur-faces, the forming tool is pivoted in such a manner as to maintain its axis of rotation perpendicular to an arcuately curved edge being shaped by the tool. To compensate for twist, the airfoil is rotated about its central axis to maintain a major side sur-face of the airfoil in abutting engagement with a positioning or locating roller disposed adjacent to the edge forming tool.
The locating roller rolls along a major side surface of the air-foil to position the edge portion of the airfoil and the forming tool relative to each other as the forming tool moves along the twisted edge.

Description

1~L833L~
sac~r-und of the Inv~ntion This invention relates generally to an apparatus for shaping aixfoils and more specifically to an apparatus for shaping the leading and/or trailing edge portions of an airfoil of the type utilized in turbines, compressors and similar fluid- -flow devices.
The leading and trailing edge portions of airfoils ;~
which are utilized in gas turbine engines have previously been finished by hand grinding or other manual finishing methods.
These manual finishing methods are relatively inaccurate and it is extremely difficult, if not impossible, to hold the radius of curvature of an airfoil edge to a very small tolerance. Since --~
the operating efficiency of a turbine engine is enhanced if the leadiny and trailing edges are accurately finished to relatively ~ ~
small tolerances, more than two hours have been previously re- ~ ;
~uired to hand shape the leading and trailing edge portions of a turbine blade. -In order to expedite the construction of an airfoil, ~nown prior art patents have disclosed various types of machines and methods for shaping either or both the leading and trailing edge portions of an airfoil. Some of these known airfoil finish-ing apparatus and methods are disclosed in U. S. Patent Nos.

2,681,500 2,680,392; and 2,336,303. Fox example, U. S. Patent No. 2,680,392 discloses an appaxatus for swaging the edge port-ion of an airfoil. However, this apparatus cannot be utilized to compensate for either bow or twist in the edge portion of the airfoil. If a cutting or milling tool was utilized in place of the swaging tool of this known apparatus, the cutting tool would not follow the contour of the edge of the blade in such a mannex ~t~4~3 ~L~

as to provide an accurately shaped blade.
Sum~ary of the Present Invention According to one aspect of the invention, ~here is provided an appa-ratus for use in s~aping an airfoil having major side surfaces interconnected by an arcuately bowed and longitudinally extending edge which bows transversely to the major side surfaces, said apparatus comprising a rotatable forming tool, means for supporting said forming tool for rotation about its central axis, ~ ~:
means for providing for engagement of said forming tool with the arcuately ~ :
bowed edge of the airfoil throughou~ the length of the arcuately bowed edg~
portion by effecting rela~ive movement be~ween said forming ~ool and airfoil while ~aintaining said forming tool in engagement with the arcuately bowed ~dge por~ion of the airfoil, and means for maintaining the central axis of said orming tool in the same angular orientatlo~ relative ~o a portion of an :
arcuately bowed lo~gitudinal central axis of tho edge portion 0~:t~2 airfoil ~;
in an area wher~ the forming tool engages the edge portio~ of thè airfoil `~
during engagement of said forming tool with the arcuately bowed edge portion ~ ~-of the airfoil throu~hout the length of the arcuately bowed edge portion of `~
the airfoil.
According to anothar aspect of the inven~ion, there is provided a ~ ~ :
:: . , ,:
method of shaping an airfoil having major side su~faces interconnected by an arcuately bowed and longitudinally extending edge portion which bows trans~
versely to the major side surfa~es, said method comprising the steps of ro-tating a forming tool about a central axis of the forming tool, engaging the arcuately bowed edge portion of ~he airfoil with the Totating fo~ming tool ::
throughout the length of the arcuately bowed edge portion of the airfoil by effecting relative movement between the airfoil and the ro~ating forming :
tool, main~aining ~he rotating forming tool in engage~ent with the arcuately bowed edge portion of the airfoil during said step of effecting relative move~ent between the airfoil and the rotating forming tool, and at least "

~41~3~9 partially compensating for the bowed configura~ion of the longitudinally ex-tending edge portion of the airfoil by maintnining the central axis of the rotating forming tool in the same angular orientation relative to a portion of an arcuately bowed longitudinal central axis of the airfoil in an area where the for~ing tool engages the edge portion of the airfoil ~Ihile perforlDing said step of effecting relative movement between the airfoil and the rotating ;-:
forming tool.
Brief Description of the Dr~wings The foregoing features of the present invention will become more 0 apparent upon a considerati~n of the following description taken in connection the accompanying dra~ings ~herein:
Fi~ure 1 i5 a schematic illustration depicting an :~

airfoil having a longitudinally tapexed configuration ~ I~. 2 is an elevational view, taken generally along the line 2-2 of FIG. 1, illustrating the bowed and twisted con~
: ~' r :;
figuration of major side surfaces of the airfoil;: . :
FIG. 3 is a fragmentary sectional view depicting the ~:
manner in which an edge portion of the airfoil of FIGS. 1 and 2 is shaped;
FIG. 4 is a pictorial illustration of an airfoil milling machine constructed in accordance with the present ~ -invention;
FIG. 5 is an elevational view, taken generally along ,~ .
the line 5-5 of FIG. 4, illustrating the relationship between a forming tool and a plurality of longitudinally extending cams which efect movement of the forming tool in such a manner as to compensate for the tapered, bowed and twisted configuration of the airfoil;
FIG. 6 is a plan view, taken generally along the line ~- :
6-6 of FIG. S, further illustrating the construction of the air-foil milling machine;
FIG. 7 (on sheet 1 of the drawings) is an enlarged fragmentary view illustrating the relationship between a cutting ~ ~;
or milling tool and a leading edge of an airfoil being shaped ~`
by the cutting tool; and :
FIG. 8 is a fragmentary sectional view, generally similar to FIG.~7 but on a somewhat smaller scale, illustrating ~ :
the relationship between a forming or milling tool and the trail-ing edge of a turbine blade being ~haped by the forming tool.
.' ^ , . . . .

3~9 ;
Description of One Specific Pref'erred __mbodiment of th_Invention An airfoil 10 is illustrat~d in FIG. 1 and has a leading edge 12 and a trailing edge 14. The edges 12 and 14 extend between a relatively wide tip end por~ion 16 and narrow root end portion 18 of the airfoil. Both the leading and trail-ing edges 12 and 14 of the airfoil have a bowed configuration.
Thus, the trailing edge 14 is arcuately bowed outwardly Erom a ~;~
straight line or axis 22 (see FIG. 2) es~tending between the tip and root end portion~ 16 and 18. The leading edge 12 of the airfoil 10 has an arcuately bowed configuration similar to the ~ ~ -configuration of the trailing edge 14.
The major side surfaces 26 and 28 of the airfoil 10 are twisted (FIG. 2). An axis 32 at the tip of the airfoil 10 extends perpendicular to the leading and trailing edges 12 and ;
14 of the airfoil. The axis 32 is offset angularly from an axis 34 extending perpendicular to the leading and trailing edges 12 and 14 of the airfoil at the root 18 of the airfoil. Of courset the extent to which the axes 32 and 34 are angularly offset `
relative to each other is determined by the extent to which the ~-20 major side surfaces 26 and 28 of the airfoil are'twisted about a longitudinally extending central axis 38 (see FIG~ 13 of the airfoil 10 The leading edge 12 of the airfoil 10 has a smoothly curved cross-sectional configuration (see FIG. 3). Thus, the leading edge 12 has a curved outex surface 42 which extends into a smooth tangential intersection with a concave major side sur~
face 26 of the airfoil 10. The intersectlon between the curved outer surface 42 and a convex major side surface 28 of the air-~ . . . ..
,,. , ~ . . .

~ 83~
foil 10 is slightly discontinuous. The obtaining of a smoothintersection between the concave major side surface 26 and the curûed surface of the leading end portion 12 of the airfoil 10 is important if an associated turbine is to have optimum operat~
ing characteristics. The slight discontinuity between the sur-face 42 and convex major side surface 28 has little or no effect on the operating characteristics of a turbine with which the blade 10 is associated.
In accordance with the present invention, an airfoil milling machine 50 (FIG. 4) is utilized to shape the leading and -trailing edges 12 and 14 of the airfoil 10. Heretofore, the leading and trailing edges of relatively long airfoils were hand sh`aped. The shaping of the leading and trailing edge~ of one known relatively long tuxbine blade required approximately two hours of careful ~and work. By utilizing the milling machine 50, ;
the leading and trailing edges of a similar turbine blade can be shaped in approximately 12 minutes. In addition, the milling machine 50 is capable of shaping the leading and trailing edges of a turbine blade to a closer tolerance than could be obtained by hand methods~ As is well known to those s~illed in the art, the operating characteristics of a turbine can be improved sub~
stantially by increasing the accuracy with which the leading and ;~
trailing edges of a turbine blade are shaped. ~`
The airfoil milling machine 50 includes a forming or milling tool 54 haviny a plurality of radially outwardly project~
ing cutting teeth 56 which are disposed in an annular array on a body portion of the forming tool. ~s the forming tool 54 is moved through a working stroke along a path extending between the tip and root end portions 16 and 18 of the turbine blade 10, ~;

: , . - ' ,, ' ' ; ~ :, :
: ,, , , , :
. , ~0~3319 ~ .a vertical or tap~r cam 60 cooperates with a follower 62 (see - -FIGS. 4 and 5~ to move the forming tool $4 in ~uch a manner as to compensate for the longitudinal taper of the airfoil 10. The cam 60 has a length which is somewhat greater than the length of the airfoil edge 12. The cam 60 is shaped so as to move the forming tool 54 v~rtically with tapering of the leading edge 12 relative to the hori.zontal central axis 38 of the air~oil 10.
As the forming tool 54 is moved along the leading ~:
edge 12 of the alrfoil 10, a longitudinally extending bow cam 66 cooperates with a cam follower 68 (së~ FIGS. 5 and 6) to :
effect pivotal movement of the forming tool 54 about a vertical axis 72 (FIG. 5) which intersects a horizontal axis 74 of rotat-ion of the forming tool. The cam 66 is longex than the airfoil ;~
10 and has a configuration such that the forming tool 54 is pivoted about the vertical axis 72 to maintain the axis 74 of rotation of the forming tool perpendicular to the arcuately bowed -~ -~
leading edge 12 of the turbine blade 10. This is illustrated schematically in FIG. 2 wherein the forming tool 54 is shown in -~
dashed lines adjacent to the tip end 16 of the turbine blade 10 and is shown in solid lines adjacent to the root end 18 of the turbine blade. As the forming tool moves between the tip and ;~
root end portions of the air~oil 10, the central axis 74 of the ~:
rotating forming tool 54 is maintained in a perpendicular relat~
ionship with a central axis of the arcuately bowed leading edge 12.
The forming tool 54 is rotated at a relatively high speed by a drive motor ~6 (FIG. 5) connected with the forming tool 54 by a tool support and drive collet or chuck 77. If the central axis 74 about which the forming tool or cutting head 54 .. . . .
, '.: : - .
,~

3~9 rotates is not maintained in a perpendicular relationship with the arcuately bowed central ax.is of the leading edge portion 12 in the manner shown sche~atically in FIG. 2, the circular arrays of generally radially projecting teeth 56 on the rotating form~
ing or milling tool 54 would nick or gouge the airfoil 10. Of course, the resulting discontinuity in the edge of the blade would impair the operating characteristics of any machine with which the airfoil is used.
Since the major side surfaces 26 and 28 of the air-foil 10 are twisted about the central axis 38, it is necessary to rotate the airfoil about its horizontal central axis to -~
maintain the edge portion 12 of the airfoil in the desired mach-ining orientation shown in FIG. 7. When the airfoil 10 is in the desired machining orientation, the leading edge 12 of the airfoil is centered relative to the forming tool 54 (FIG. 7) ;;
and the vertical axis 72 extends through the center of the port- ~.
ion of the leading edge 12 engaged by the forming tool. To facilitate rotational movement of the alrfoil 10 about its central axis 38, the tip portion 16 of the airfoil is mounted in a rotatable tailstock 80 and a root end poxtion 18 of the airfoil is engaged by a rotatable headstock 82. A ~lu~d pres-sure actuated torque motor 84 i5 connected ~o the headstock 82 and continuously urges the headstock to rotate the air~oil about its horizontal central axis 38 in the direction of the arrow 86 in FIG. 4.
The continuous biasing force applied to the headstock 82 by the torque motor 84 presses the concave major side surface ;
26 of the airfoil agains~ a circular positioning or locating sur-face 90 (see FIG. 7) on a rotatable roller or disc 92. The .. . . . .
~ ?

3:~
roller 92 is mounted fo~ rotation about a vertical a*is which .i9 parallel to and spaced apart from the axis 72. The circular ~ -outer surface 90 of the roller 92 engages the major side surface 26 of the airfoil 10 immediately beneath the forming tool 54. - -A line of rolling engagement of the locating surface 90 with the surface is always disposed in a flat plane containing the axes 72 and 74 A cam follower 94 (FIGS. 5 and 6) engages a twist `
or roll cam 96 to effect horizontal movement of a feed table 98 to position the locating roller 92 in such a manner that the leading edge 12 of the airfoil 10 is always centered relative to :~
the forming tool 54 as the forming tool is moved along the lead~
ing edge. Of course, the cam 96, like the cams 60 and 56, has a `; ;
length which is greater than the length of the airfoil 10.
When the leading edge 12 of the airfoil 10 is to be shaped to a desired cross sectional configuration, such as shown in FIG. 3, the tip end 16 of the airfoil is gripped by the tail-stock 80 while the root end 18 of the airfoil is supported by the headstock 82. At this time, the cutting tool 54 is axially :
spaced from the tlp end 16 of the airfoil (as shown in FIG. 4)~
The leading edge 12 of the airfoil 10 is then manually moved into alignment with the cutting tool 54 (as shown in FIG. 7).
When the cutting tool 54 has been aligned with lead-ing edge 12, the concave major surface 26 of the airfoil 10 is pressed against the roller 92 under the influence of the torque motor 84. The roller 92 centers the airfoil relative to the forming tool 54 so that the axially inner set of teeth 88 on the cuttlng tool 54 extend into a smooth tangential engagement with the concave major surface 26 of the airfoil 10. An outer set of _g_ ,~..... . .. ; , . .
' . . ' , ', : '~', ;:, 3~
teeth 90 on the forming tool 54 engage the convex major side surface 28 of the airfoil 10. The leading edge 12 can then he shaped to a smooth arcuate configuration, such as shown in FIG.
3, by the profile of the portions of the cuttiny teeth which extend between the inner and outer sets of teeth 88 and 90.
The cam 96 is shaped to effect horizontal movement of the follower 94 and roller 92 to maintain the cutting tool 54 centered relative to the twisted edge 12 of the airfoil 10 as the cutting tool is moved along the edge 12. The cam follower 94 is ~ .
mounted on a feed table 98 tFIG. 5). The feed table 98 is reciprocated along a horizontal path toward and away from the horizontal central axis 38 of the airfoil 10 by the interaction between the cam 96 and follower 94 as the forming tool 54 is moved ; ~ ~;
through a working stroke along the edge 12 of the airfoil 10. As the forming tool 54 moves through a working stroke, the locating roller 92 rolls along the surface 26 of airfoil 10. When this is -~
occurring, the follower 94 is continuously pressed against the cam 96 by a piston and cylinder assembly 100 connected with the feed table 98 and a slide assembly 102.
As the forming tool 54 is moved through a working stroke along the leading edge 12 of the airfoil 10, the vertical or taper cam 60 cooperates with the follower 62 to actuate the slide assembly 102 (FIG. 5) to position the feed table 98 vertic~
ally. The slide assembly 102 includes vertical posts 103 on whlch a feed table guide section 104 of the slide assembly is slidably mounted by ball bushings 106 and held downwardly against the cam .
60 by gravity. Therefore, the roller 62 is continuously pressed against the vertical or taper cam 60 and the vertical position of the feed table 98 and forming tool 54 is regulated by the taper -10~

.... . , , : . ,,, , . ... ~ ' ~

3i~

cam 60. Two piston and cylinder assemblies (not shown but sim-ilar to the piston and cylinder assembly 100) are connected bet-ween the feed table guide section 104 and a taper cam 60 upon command to raise the assembly and disengage the ~orming tool 54 in the return stroke.
At this time the forming tool 54 is positioned with the horizontal axis 74 of rotation o:E the forming tool 54 extend-ing perpendi~ular to a central longitudinal axis of the arcuately bowed edge portion 12 of the airfoil 10 by the cooperation between the cam follower 68 and the cam 66. ~he cam follower 68 is con-tinuously pressed against the cam 66 by a piston and cylinder assembly 110 (FIG. 6) which is mounted on an upstanding suppo~t section 112 connected to the rotating head 112. A forming tool ;~-support bracket 114 (FIG. 5~is pivotally connected at 116 with the support ~ection 112 for rotation about the vertical axis 72. The forming tool drive motor 76 is mounted on the bracket 114 and ~ :
moves with the braclcet as the forming tool 54 is pivoted about the axis 72. An actuator rod or shaft 118 extends through the piston and cylindex assembly 110 and is connected at one end with the cam follower 68. The other end of the actuator rod 118 is pivotally connected with an outwardly projecting arm 120 on the support bracket 114 (~ee FIGS. 5 and 6). The actuator rod 118 is connected with a piston 110 and is anchored in position by clamp bracket 122 so that air pressure on the piston continuously presses the cam ollo~er 68 against the cam 66.
When the forming tool 54 has been oriented in align-ment with the leading edge 12 of the airfoil 10 in the manner ;~
shown in FIG. 7, a drive motor 123 (FIG. 4) is energized ro :
rotate a longitudinally extending lead screw 124 (FIG. 5~ which ~ ~

: . , , : , ,. . . . . . .
:., ,, : ., , 3~
moves the slide a~sembly 102 along linear horizontal ways 125 and 126 adjacent to a base 128. Aq the slide assembly 102 is .
moved along the longitudlnal ways 125 and 126, the ~orming tool 54 move~ along a longitudinally extending path to the lPading edge 12 of the airfoil 10. As the forming tool 54 moves along this path through a work stroke, the taper cam 60 and cam follow- :
er 62 cooperate with the slide assembly 102 to move the feed table ;~
98 vertically to compensate for the longitudinal taper of the airfoil 10. Although the work stroke could be in either direct-ion, the work stroke is from the relatively wide tip end portion ~ :
16 of the airfoil 10 toward the relatively nàrrow root end port- :
ion 18 of the airfoil. Therefore, cam 60 slopes downwardly so that the cutting tool 54 is moved inwardly toward the central ~ ~
:' ' ::.
axis 38 of the airfoil 10 as the cutting tool 54 moves along the leading edge 12. .
Simultaneously with this vertical movement of the cutting tool 54 to compensate for the tapered configuration of the airfoil 10~ the cutting tool 54 is pivoted about the vertical axis 72 under the influence of the ~am 66 to maintain the axis 74 of rota-tion of the cutting tool perpendicular to an arcuately -::;
curved cent~al axis of the bowed leading edge 12 of the airfoil 10~ Thus as the cutting tool 54 is moved through a work stroke along the leading edge 12 of the airfoil, the cam 66 moves the ~-~
cam follower 68 to pivot the forming tool and motor support mounting 114 about the pivot connection 116 which is coaxial with the vertical axis 72. The cam 66 has a configuration such that the horizontal central axis 74 of the forming tool 54 is main- `
tained perpendicular to the arcuately bowed longitudinal central axis of the leading edge portion 12. It should be noted that the ,. " '' :~ ' ' . . , ,--. . ~ ~ ., ~

~q~4~ 9 cams 66 and 96 have vertical extents sufficient to accommodate vertical movement of the associated followers 68 and 94 upon movement of the feed table 98 under the influence of the taper cam 60. .~:.
During the pivotal movement of the forming tool 54 about the vertical axis 72 under the in~luence of the cam 66 and the forming tool 54 due to the action of the cam 60, the forming tool is moved in and out with the locating roller 92. This move~
ment of the forming tool 54 and locating roller 92 under the in~
fluence of the cam 96 is along a horizontal path in a direction perpendicular to the axis 38. This moves the positioning or lo~
cating roller 92 to compensate for the twisted configuration of :~
the airfoil 10. ~ :
As the locating roller 92 is moved in and out under the influence of the cam g6, the torque motor 84 is continuously attempting to rotate the airfoil 10 about its horizontal central axis 38 to press the concave major side surface 26 of the airfoil against the locating roller 92. This maintains the leading edge 12 of the airfoil in a centered relationship with the two annular -arrays 88 and 90 of radially projecting teeth on the cutting tool 54 (see FIG. 7) as the cutting tool is moved through a work stroke along the leading edge 12 of the airfoil 10. During the work stroXe, the positioning roller 92 rolls along the major side surface of the airfoil 10 to maintain the desired spatia~ relat~
ionship between the forming tool 54 and the air~oil. Thus, the forming tool 54 and the leading edge 12 of the airfoil 10 are positioned transversely relative to each other by the locating ::~;
roller 92 which rolls along the concave major side sur~ace 26 of the airfoil.

, -13- :

.''",' ', ' ''' . : , ' ''' ` ,'',', ' ~ :
': : ~ . . .. .
. .

:~4~3151 After the leading edge 12 of the airfoil 10 has been shaped to the desired configuration by a single work stroke of the cutting tool ~4 in the manner previously explained, the trail-ing edge 14 of the airfoil is shaped to the desired configuration.
In order to enhance the operating characteristics of a ~as turbine engine with which the airfoil 10 is to be associated, it is nec-essary to provide an extremely smooth line of intersection between the concave major side surface 26 of the airfoil 10 and the round~
ed surface which defines the exterior of the trailing edge portion. -~
Therefore, it is necessary to center the trailing edge 14 of the airfoil 10 relative to a forming tool by engaging the concave major side surface 26 of the airfoil with the locating or posit-ioning roller 92 adjacent to the trailing edge portion L4 of the airfoil.
To center the trailing edge 14 relative to a trailing edge forming tool 54a (FIG. 8), the locating roller 92 is mounted on an arm 136 which extends outwardly from the motor support bracket 114. The trailing edge forming tool 54a has two annular arrays 88a and 90a of generally radially projecting cutting teeth. ~-Since the locating roller 92 is disposed outwardly of the concaveinner surface 26 of the airfoil 10, the direction of operation of the torque motor 84 is reversed so that the torque motor rotates the airfoil 10 about the central horizontal axis 38 in the direct~
ion of the arrow 138 in FIG. 4. Thereafter, the torque motor 84 presses the concave major side surface 26 of the airfoil 10 left-wardly (as viewed in FIG. 8) against the circular exterior surface of the roller 92.
The vertical cam 60, bow cam 66 and twist cams 96 are replaced with suitable cams corresponding to the configuration of ~14-: . . , 33~9 the trailing ed~e portion 14 of the airfoil 10. The milling machine 50 is then operated in the mannex previously explained in connection with the shaping o the leading edge portion 12 of the airfoil 10 to shape the trailing edge portion 14 of the air- ~
foil. It should be noted that during the shaping of the trailing ` ~;
edge portion 14 of the airfoil the cams 60, 66 and 96 cooperate with the cam followers 62, 68 and 94 in the same manner as pre~
viously explained in connection~with the shaping of the leading edge 12 of the airfoil 10. However, the torque motor 84 tends to rotate the airfoil 10 in the opposite direction about the central axis 38 to thereby press the concave inner surface 26 of the airfoil against the forming roller 92 which is now dis~
posed on the outside of the airfoil 10 as shown in FIG. 8.
Although the forming tool 54 has been described herein as being moved under the influence of the cams 60, 66 and 96 to ;
compensate for the tapered, bowed and twisted configuration of the airfoil 10, it is contemplated that the forming tool can be ~ ,~
moved under the influence of other known devices. For example, it is contemplated that numerical controls could be utilized to effect movement of the ~orming tool under the influence of various servo-motors in accordance with a prerecorded program.
It should also be noted that although the forming tool 54 has been disclosed herein as being a milling cutter o the arbor type, other types of known forming tools could be utilized if desired. While the airfoil milling machine 50 is capable of shap-ing an airfoil 10 having a tapered, bowed and twisted configurat-ion, it is contemplated that the airfoil milling machine could be utilized to shape the edges of an airfoil having only one or two of these configurations. For example, the airfoil milling machine ;~ ~

-15- ~ -". " .- - , , . .. " . , , , . , . , . , ~

33~
50 could be utilized to shape the leading and trailing edges of an airfoil having a twisted and tapered configuration or to shape the leading or trailing edges of an airfoil having a bowed configuration.

, . . .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for use in shaping an airfoil having major side surfaces interconnected by an arcuately bowed and longitudinally extending edge which bows transversely to the major side surfaces, said apparatus comprising a rotatable form-ing tool, means for supporting said forming tool for rotation about its central axis, means for providing for engagement of said forming tool with the arcuately bowed edge of the airfoil throughout the length of the arcuately bowed edge portion by effecting relative movement between said forming tool and airfoil while maintaining said forming tool in engagement with the arcuately bowed edge portion of the airfoil, and means for main-taining the central axis of said forming tool in the same angul-ar orientation relative to a portion of an arcuately bowed longitudinal central axis of the edge portion of the airfoil in an area where the forming tool engages the edge portion of the airfoil during engagement of said forming tool with the arcuately bowed edge portion of the airfoil throughout the length of the arcuately bowed edge portion of the airfoil.

2. An apparatus as set forth in claim 1 wherein said means for maintaining the central axis of the forming tool the same angular orientation relative to an arcuately bowed long-itudinal axis of the edge portion of the airfoil including means for varying the angular orientation of the central axis of the forming tool relative to a straight line extending between opposite ends of the arcuately bowed edge portion of the airfoil during relative movement between said forming tool and the arcuately bowed edge portion of the airfoil.

3. An apparatus as set forth in claim 2 wherein said means for varying the angular orientation of the central axis of said forming tool includes means for moving said form-ing tool about a secondary axis extending transversely to the central axis of said forming tool to change the angular orient-ation of the central axis of said forming tool relative to the straight line extending between opposite ends of the arcuately bowed edge portion of the airfoil and thereby maintain the same angular orientation between the central axis of said forming tool and the arcuately bowed longitudinal axis of the edge por-tion of the airfoil during relative movement between said form-ing tool and the arcuately bowed edge portion of the airfoil.

4. An apparatus as set forth in claim, 1 further including positioning means for engaging a major side surface of the airfoil at a location adjacent to said forming tool, said positioning means including an arcuate positioning surface which is spaced apart from said secondary axis and which has a central axis extending parallel to said secondary axis.

5. An apparatus as set forth in claim 4 further including means for urging the major side surface of the airfoil into abutting engagement with said arcuate positioning surface.

6. An apparatus as set forth in claim 2 wherein said means for varying the angular orientation of the central axis of said forming tool includes means for moving said forming tool about a secondary axis extending perpendicular to the central axis of said forming tool to maintain the central axis of said forming tool perpendicular to the arcuately bowed longitudinal axis of the edge portion of the airfoil during relative movement between said forming tool and the arcuately bowed edge portion of the airfoil.

7. An apparatus as set forth in claim 2 wherein said forming tool includes a plurality of cutting teeth mounted in a circular array, said apparatus further including drive means for rotating said circular array of cutting teeth about the central axis of said forming tool as said forming tool and airfoil move relative to each other.

8. An apparatus as set forth in claim 7 wherein said means for varying the angular orientation of the central axis of said forming tool includes means for moving said forming tool about a secondary axis extending transversely to the axis of rotation of the circular array of cutting teeth to change the angular orientation of the axis of rotation of the circular array of cutting teeth relative to the straight line extending between opposite ends of the arcuately bowed edge portion of the airfoil and maintain a substantially constant relationship between the circular array of cutting teeth and the edge portion of the airfoil as said forming tool and airfoil move relative to each other.

9. An apparatus as set forth in claims 1 or 2 further including positioning means for engaging a major side surface of the airfoil adjacent to said forming tool to at least partially position the arcuately bowed edge portion of the airfoil and forming tool relative to each other, and means for rotating the airfoil about its central axis to maintain the major side surface of the airfoil in abutting engagement with said positioning means as said forming tool and airfoil move relative to each other.

10. An apparatus as set forth in claim 1 further including means for moving said forming tool along a longitud-inally extending path adjacent to said longitudinally extending edge portion of the airfoil, locating means disposed adjacent to said forming tool and movable along the longitudinally ex-tending path with said forming tool for locating said forming tool and said one longitudinally extending edge portion of the airfoil relative to each other as said forming tool moves along the longitudinally extending path, said locating means including a roller having a circular outer surface which is disposed in rolling engagement with a major side surface of the airfoil as said forming tool moves along the longitudinal extending path and means for supporting said roller for rotation about a second axis extending transversely to the central axis of said forming tool, said means for maintaining said forming tool in the same angular orientation relative to the airfoil including means for moving said forming tool about a third axis extending trans-versely to said first axis to maintain said first axis in the same angular orientation relative to an arcuately bowed central axis of the edge portion of the airfoil as the forming tool moves along the longitudinally extending path.

11. An apparatus as set forth in claim 10 wherein said forming tool includes cutter means for milling said one longitudinally extending edge portion of the airfoil to a predetermined cross sectional configuration, said circular outer surface of said roller being located a predetermined distance from said cutter means to maintain a predetermined spatial relationship between said cutter means and a major side surface of the airfoil as said forming tool means moves along the longitudinally extending path.

12. An apparatus for use in shaping an airfoil, said apparatus comprising forming tool means for forming at least one of a pair of arcuately bowed and longitudinally extending edge portions of an airfoil, means for moving said forming tool means along a longitudinally extending path adjacent to said one arcuately bowed and longitudinally extending edge portion of the airfoil, means for rotating said forming tool means about a first axis as said forming tool means moves along the longitudinally extending path, and means for pivoting said form ing tool means about a second axis extending transversely to said first axis to maintain said first axis perpendicular to an arcuately bowed central axis of said one edge portion of the air-foil as said forming tool means moves along the longitudinally extending path.

13. An apparatus as set forth in claim 12 further including locating means disposed adjacent to said forming tool means and movable along the longitudinally extending path with said forming tool means for locating said forming tool means and said one longitudinally extending edge portion of the air-foil relative to each other as said forming tool means moves along the longitudinally extending path.

14. An apparatus as set forth in claim 13 wherein said locating means includes a roller having a circular outer surface which is disposed in rolling engagement with a major side surface of the airfoil as said forming tool means moves along the longitudinally extending path.

15. An apparatus as set forth in claim 13 further including means for supporting said roller for rotation about a third axis extending parallel to said second axis.

16. An apparatus fox use in shaping at least one of a pair of longitudinally extending edge portions of a longitud-inally tapered airfoil having twisted and bowed major side sur-faces extending between and interconnected by the longitudinally extending edge portions from a tip portion to a root portion of the airfoil, said apparatus comprising tool means for engaging said one longitudinally extending edge portion of said airfoil, and means for effecting movement between said tool means and the one longitudinally extending edge portion of the airfoil while maintaining said tool means in engagement with the one longitud-inally extending edge portion of the airfoil to thereby shape the one longitudinally extending edge portion of the airfoil with said tool means, said means for effecting movement between said tool means and the one longitudinally extending edge portion of the airfoil including means for compensating for the longitudinal taper of the airfoil by varying the distance be-tween said tool means and a longitudinal central axis of the airfoil during engagement of said tool means with the one longit-udinally extending edge portion of the airfoil, means for compensating for the bowed major side surfaces of the airfoil by maintaining a predetermined spatial relationship between an arcuately curved and longitudinally extending axis of the airfoil and said tool means during engagement of said tool means with the one longitudinally extending edge portion of the airfoil, and means for compensating for twist of the major side surfaces of the airfoil by effecting relative movement between the airfoil and said tool means in a direction transverse to the longitudinal axis of the one longitudinally extending edge portion during engagement of said tool means with the one longitudinally extending adge portion of the airfoil.

17. An apparatus for use in shaping at least one of a pair of longitudinally extending edge portions of a long-itudinally tapered airfoil having twisted and bowed major side surfaces extending between the longitudinally extending edge portions from a tip portion to a root portion of the airfoil, said apparatus comprising tool means for engaging said one longitudinally extending edge portion of said airfoil, and means for effecting movement between said tool means and the one longitudinally extending edge portion of the airfoil to thereby shape the one longitudinally extending edge portion of the airfoil with said tool means, said means for effective move-ment between said tool means and the one longitudinally extend-ing edge portion of the airfoil includes means for moving said tool means along a longitudinally extending path disposed adjac-ent to the one edge portion of the airfoil and having a length which is at least as great as the distance between the tip and root portions of the airfoil, said means for effecting move-ment between said tool means and the one longitudinally extend-ing edge portion of the airfoil further including means for compensating for the longitudinal taper of the airfoil by varying the distance between said tool means and a longitudinal central axis of the airfoil during engagement of said tool means with the one longitudinally extending edge portion of the air-foil, means for compensating for the bowed major side surfaces of the airfoil by maintaining a predetermined spatial relation-ship between an arcuately curved and longitudinally extending axis of the one longitudinally extending edge portion and a central axis of said tool means during engagement of said tool means with the one longitudinally extending edge portion of the airfoil, said means for compensating for the bowed major side surfaces of the airfoil including a longitudinally extending cam disposed adjacent to said longitudinally extending path and having a length which is at least as great as the distance between the tip and root portions of the airfoil, and cam follow-er means disposed in engagement with said cam and connected with said tool means for effecting pivotal movement of said tool means about an axis extending transversely to the arcuately curved and longitudinally extending axis of the one edge portion of the air-foil as said tool means moves along the longitudinally extending path, and means for compensating for twist of the major side surfaces of the airfoil by effecting relative movement between the airfoil and said tool means in a direction transverse to the longitudinal axis of the one longitudinally extending edge por-tion during engagement of said tool means with the one longitud-inally extending edge portion of the airfoil, said means for compensating for twist of the major side surfaces of the airfoil includes a longitudinally extending second cam disposed adjacent to said longitudinally extending path and having a length which is at least as great as the distance between the tip and root portions of the airfoil, and second cam follower means disposed in engagement with said second cam and connected with said tool means for effecting movement of said tool means in a first direction extending transversely to the longitudinally extending path and the one edge portion of the airfoil as said tool means moves along the longitudinally extending path.

18. An apparatus as set forth in claim 17 wherein said means for compensating for taper of the airfoil includes a longitudinally extending third cam disposed adjacent to said longitudinally extending path and having a length which is at least as great as the distance between the tip and root portions of the airfoil, and third cam follower means disposed in engage-ment with said third cam and connected with said tool means for effecting movement of said tool means in a second direction extending transversely to said first direction and the one edge portion of the airfoil as said tool means moves along the longitudinally extending path.

19. A method of shaping an airfoil having major side surfaces interconnected by an arcuately bowed and longitudinally extending edge portion which bows transversely to the major side surfaces, said method comprising the steps of rotating a forming tool about a central axis of the forming tool, engaging the arcuately bowed edge portion of the airfoil with the rotating forming tool throughout the length of the arcuately bowed edge portion of the airfoil by effecting relative movement between the airfoil and the rotating forming tool, maintaining the rotating forming tool in engagement with the arcuately bowed edge portion of the airfoil during said step of effecting relative movement between the airfoil and the rotating forming tool, and at least partially compensating for the bowed config-uration of the longitudinally extending edge portion of the airfoil by maintaining the central axis of the rotating forming tool in the same angular orientation relative to a portion of an arcuately bowed longitudinal central axis of the airfoil in an area where the forming tool engages the edge portion of the airfoil while performing said step of effecting relative movement between the airfoil and the rotating forming tool.

20. A method as set forth in claim 19 wherein said step of maintaining the central axis of the forming tool in the same angular orientation relative to a portion of an arcu-ately bowed longitudinal central axis of the airfoil includes the step of pivoting the rotating forming tool about a second axis extending transversely to the central axis of the rotating form-ing tool to vary the angular orientation of the central axis of the rotating forming tool relative to a straight line extending between opposite ends of the arcuately bowed edge portion of the airfoil while performing said step of effecting relative movement between the airfoil and the rotating forming tool.

21. A method as set forth in claims 19 or 20 further including the step of rotating the airfoil about a longitudin-ally extending axis disposed between longitudinally extending edge portions of the airfoil while performing said step of effecting relative movement between the airfoil and the rotat-ing forming tool.

22. A method as set forth in claims 19 or 20 wherein said step of maintaining the central axis of the forming tool in the same angular orientation relative to a portion of an arcuately bowed longitudinal central axis of the airfoil in-cludes the step of maintaining the central axis of the forming tool perpendicular to the portion arcuately bowed longitudinal central axis of the edge portion of the airfoil in the area where the forming tool engages the airfoil while performing said step of effecting relative movement between the airfoil and the rotating forming tool.

23. A method as set forth in claims 19 or 20 further including the step of engaging a major side surface of the airfoil to position the rotating forming tool and bowed edge portion of the airfoil relative to each other while performing said step of effecting relative movement between the airfoil and the rotating forming tool.

24. A method as set forth in claims 19 or 20 further including the step of at least partially compensating for a tap-ered configuration of the airfoil by varying the distance be-tween the central axis of the forming tool and a central axis of the airfoil while performing said step of effecting relative movement between the airfoil and the rotating forming tool.

25. A method as set forth in claim 19 further including the step of locating the rotating forming tool relat-ive to the arcuately bowed edge portion of the airfoil by con-tinuously engaging a major side surface of the airfoil with a locating surface disposed in a predetermined location relative to the forming tool while performing said step of effecting relative movement between the airfoil and the forming tool.

26. A method as set forth in claim 25 wherein said step of engaging a major side surface of the airfoil with a locating surface includes the step of rolling a circular locat-ing surface along the major side surface of the airfoil while performing said step of effecting relative movement between the airfoil and rotating forming tool.